In recent years, a demand for an extensible flexible printed circuit board in which a flexible printed circuit board has extensibility increases. Some extensible flexible printed circuit boards are used as a component of, for example, so-called a wearable electronic device attached to a human body or clothing in addition to a robot performing a variety of motions.
In the wearable electronic device, there is a case when it is attached to a bending portion of a human body such as, for example, a joint or the like, and it is necessary to consider capability of bending and twisting of the wearable electronic device to enable the attachment to the bending portion as stated above. Besides, it is necessary to consider a waterproof property when attaching to the human body.
There are technical contents disclosed in, for example, Patent Literatures 1 to 4 to correspond to requirements as stated above. In Patent Literatures 1 to 4, there is disclosed a configuration in which a land pattern and a wiring layer (an extensible pattern) are provided at an extensible insulating base material, and the wiring layer is covered by an extensible insulating layer.